% Jiaxi He
% Swinburne University of Technology
% jiaxihe@swin.edu.au

function d = Dx(u)
[rows,cols] = size(u); 
d = zeros(rows,cols);
d(:,2:cols) = u(:,2:cols)-u(:,1:cols-1);
d(:,1) = u(:,1)-u(:,cols);
return

